A Code Division Multiple Access (CDMA) 1×/EVDO hybrid access terminal (mobile device) is a device which operates in a hybrid fashion that supports both CDMA 1× and EVDO radio access technologies (RATs). EVDO stands for Evolution Data Only or Data Optimized and, as suggested by this, is a data only system. EVDO is alternatively known as High Rate Packet Data (HRPD). One advantage of an EVDO system is that it allows a higher transfer rate for data. EVDO networks are also useful to carriers to free CDMA 1× system voice capacity by removing data traffic from the CDMA 1× system.
A mobile device operating in a CDMA 1×/EVDO hybrid mode will first acquire either an EVDO network or a CDMA 1× network, and once this network has been acquired and it is in an idle state the mobile device will then try to acquire an associated 1× network or an associated EVDO network respectively.
In order to acquire the EVDO system, an access network (AN) authentication must occur through an A12 interface. A12 is the interface that carries signaling information related to access authentication between the Session Controls/Mobility Management (SC/MM) functions in the AN and the AN-AAA (Access Network-Authentication, Authorization and Accounting Entity). AN authentication uses a Challenge-Handshake Authentication Protocol (CHAP) to authenticate a mobile device. AN authentication occurs upon the mobile device first attempting to access the access network and establish an initial EVDO session and is repeated after a session timeout or the access network fails to reach the mobile device after a keep alive timer expires. A12 interfaces are described in the Third Generation Partnership Project 2 (3GPP2) A.S0008 specification, the contents of which are incorporated herein by reference.
If AN authentication fails, the mobile device will periodically attempt to connect with the EVDO network to establish an EVDO session. The repetition of connection attempts wastes network resources and battery life on the device since the authentication failure likely signals future authentication failures. In addition, the repeated attempts to authenticate AN may delay data session setup on a CDMA 1× network, potentially resulting in a poor user experience.
Similarly, for devices that support a hybrid mode of other RATs operating under multiple networks, authentication on a first network may fail. Repetition of connection attempts to that network waste resources. For example, a connection to a Long Term Evolution (LTE) network may be attempted, and may fail. Further connection attempts to the LTE network may waste resources and may delay data session setup on networks of different RATs found over the air.